Pen tip structure

ABSTRACT

A pen tip structure for a ball point includes a ball socketed between a pipe tip and the end of an inner core, the end of the inner core having a flat center surface for supporting the ball and an annular lip which flares outwardly from the flat center surface to create a capillary gap between the ball and the pipe tip. Ink is supplied to the ball from a capillary ink flow channel between the inner core and the pipe.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates to a pen tip structure which includes a rotatableball socketed between the lip of the pipe and the end of an inner core.

2. The Prior Art

Ball point pens in which the ball at the pen tip part is rotated byfrictional resistance during its writing movement so as to draw ink forwriting are in, wide use throughout the world. One such known ball pointpen utilizes a pen tip structure composed of a ball bearing shaft, aball holding part within the ball bearing shaft, and a rotatable ballsocketed between a bottom surface of the ball holding part and the tipof the ball bearing shaft, the bottom surface of the ball holding partbeing conically shaped and having an ink passage at its apex. Anotherknown pen tip structure is constructed as shown in FIG. 47, wherein aball receiving core (51) having a flat bottom surface is fixed in a ballholding pipe (50), with an axial ink passage space (52) being formedtherebetween, and a ball (54) is rotatably held in a ball wrapping part(53) which communicates with the ink passage space (52). However, a pentip structure which utilizes a ball holding part having a conical bottomsurface has the following disadvantages:

PROBLEMS IN MANUFACTURING

There are some problems in machining and forming of the ball holdingpart and an ink passing hole, that is, a high precision in the cuttingoperation is required in case the ball receiving shaft is made of metal,and a forming mold with a high machining accuracy is required in casethe ball receiving shaft is made of plastic material.

PROBLEMS IN ROTATION OF BALL

There are some problems in the writing operation of the pen tip causedby the conical shape of the bottom surface of the ball holding part;that is, the rotation of the ball will be hindered due to a wedgingaction caused by its biting into the conical bottom surface inproportion to its writing pressure. The result is a poor ink drawingcharacteristic and a blurred writing phenomenon. This type of pen tipstructure is not suitable for a high speed writing operation.

On the other hand, a pen tip structure wherein the ball holding part hasa totally flat bottom surface has the following disadvantages:

PROBLEMS IN INK GUIDING OPERATION

The ball receiving part in the ball receiving core (51) at the ballwrapping part (53) may generate a so-called capillary guiding vacantarea (61) where no link capillary guiding action is performed in a space(60) formed among an outer side part (57) of the flat bottom surface(56), a surface part (58) of a ball (54) near the outer side and aninner surface part (59) of the ball holding pipe (50). This capillaryguiding vacant area (61) may hinder capillary movement of the ink alongthe surface (58) of the ball (54) and reduce or eliminate the scrapingof ink on the surface (58) while the ball (54) is rotated. Thisphenomenon may occur due to an air winding phenomenon caused by rotationof the ball and a forming of the capillary guiding vacant area (61) dueto accumulation of air in the area (60) fed into the ball wrapping part(53). As a result, the holding capacity of the ink in the ball wrappingpart (53) is decreased, a drain-back may occur, a blurring of the inkmay occur during initial writing, a poor return-back characteristic ofink may occur after the pen tip has been inverted, the supply of ink tothe ball will be unstable, excessive blurring of the ink duringhigh-speed writing will occur, and the ink may not follow a rapid changein writing direction.

In view of the facts described above, it is an object of the presentinvention to provide a pen tip structure having no problems of theconventional type of pen tip structure in which all anti-drain backcharacteristic of ink, initial writing feature, a return-back feature ofink, high-speed writing characteristic, a stable ink supplying feature,a rotating feature of the ball and a manufacturing characteristic of theball are superior.

It is another object of the present invention to provide a pen tipstructure in which a projecting wall of the pen tip structure is formedat an outside portion of a ball receiving core and the ink capillaryguiding capability in the ball wrapping part is improved.

It is yet further object of the present invention to provide a pen tipstructure in which projecting walls are formed at the outside part ofthe ball receiving core and the inner surface of the ball holding pipe,an ink capillary guiding capability in the ball wrapping part and arotational lubrication of the lubricant of ink in respect to the ballare improved.

It is a further object of the present invention to provide a pen tipstructure in which a cross-sectional area of the ink passing space isformed in a certain ratio without changing the ink capillary spacerather than a cross sectional area of the capillary guiding passage andan ink capillary guiding ratio in the ink passing space in respect tothe ball wrapping part is improved.

It is still further object of the present invention to provide a pen tipstructure in which an ink passing space is formed between an outersurface of a ball receiving core having a larger diameter than that ofthe ball and an inner surface of the ball holding pipe facing to theouter surface so as to improve the amount of ink capillary guidingvolume in the ink passing space in respect to the ball wrapping part andthe capillary guiding capability.

It is a still further object of the present invention to provide a pentip structure in which the ink passing space is formed between asubstantial trapezoid tapered outer surface having a top surface of theball receiving part in the ball receiving core and the inner surface ofthe ball holding pipe parallel to the outer surface, and both the inkcapillary guiding volume in the ink passing space in respect to the ballwrapping part and a capillary guiding control capability are improved.

It is a yet further object of the present invention to provide a pen tipstructure in which an inner diameter of the ball holding pipe is made tohave substantially the same diameter as that of the ball up to the inkpassing space forming part except the metering part where the ball isprevented from being pulled off and the diameter of the extremity end ofthe pen which is approximate to the ball diameter is improved.

It is a still further object of the present invention to provide a pentip structure in which a cross sectional shape at a diameter part of aninner surface of the ball holding pipe and a contour shape of a crosssectional shape at a diameter part of the ball receiving core aresimilar and the ink guiding capability at each of the ink passing spacesis improved.

It is a yet further object of the present invention to provide a pen tipstructure in which a cross sectional shape at a diameter part of aninner surface of a ball holding pipe and a contour shape of a crosssectional shape at a diameter of the ball receiving core are circular soas to stabilize the ink guiding capability in the ink passing space.

It is a yet further object of the present invention to provide a pen tipstructure in which a ball receiving core is formed with a spiral grooveaxially extending along an ink passing space forming part at itscircumferential surface so as to improve the axial flow yieldingcapability of ink in the ink passing space.

It is a still further object of the present invention to provide a pentip structure in which a ball receiving core has some parallel axialannular grooves in a circumferential direction at an outer surface partacting as an ink passing space so as to highly improve the axialyielding capacity of ink in the ink passing space.

It is a yet further object of the present invention to provide a pen tipstructure in which a ball receiving core has an ink capillary guidinggroove communicating with the ink passing space and reaching to a partnear the ball receiving part so as to improve the rotational lubricatingcharacteristic of the ball.

It is a still further object of the present invention to provide a pentip structure in which a ball receiving core is fixed within a ballholding pipe so as to improve a connection between the ball holding pipeand the ball receiving core.

It is a yet further object of the present invention to provide a pen tipstructure wherein a fitting part of the pen tip structure is formed as aprojection part extending axially so as to improve the bending strengthof the pen tip and the axial ink guiding capability in the ink passingspace.

It is still further object of the present invention to provide a pen tipstructure in which a fitting part of the pen tip structure is formed asa metering shape extending along a circumference of the structure so asto improve the ink guiding capability in a circumferential direction ofthe ink passing space.

It is still further object of the present invention to provide a pen tipstructure in which a ball of the pen tip structure is formed as a ballshape so as to improve its directional characteristic, its angle writingability and its general writing operation.

It is a still further object of the present invention to provide a pentip structure in which a ball holding pipe, a ball receiving core and aball of the pen tip structure are mainly made of the same high hardnessmaterial.

It is a yet further object of the present invention to provide a pen tipstructure in which a ball holding pipe, a core part in a ball receivingcore and a ball of the pen tip structure are mainly made of the samehigh hardness material and the side surface of the core part is coatedwith a synthetic resin film so as to improve its electrostatic actionand its ink wetting action.

It is a still further object of the present invention to provide a pentip structure in its which a capillary interval in ink passing space issubstantially formed to have a size of 25 to 100μ so as to improve itsink guiding capability.

It is a still further object of the present invention to provide a pentip structure in which a capillary interval of the capillary guidingpassage is made to have a value of about 25 to 100μ so as to improve itsink guiding capability.

It is a yet further object of the present invention to provide a pen tipstructure in which a space between an opening edge of a metering part ina ball wrapping part and a ball surface is made to have a value of about5 to 15μ so as to improve its ink drawing volume at the opening edge andits air winding volume.

It is a still further object of the present invention to provide a pentip structure in which a capillary guiding groove of a ball receivingcore is made to have a groove width value of about 25 to 110μ and with adepth of about 100 to 20μ so as to improve its range of ink guidingcapability.

SUMMARY OF THE INVENTION

In detail, the pen tip structure of the present invention is made suchthat a ball receiving core is fixed in a ball holding pipe, a ball isrotatably supported in the ball wrapping part and at the same time theink passing space communicating with the ball wrapping part is formed insuch a way that the ink is axially moved in a capillary form between theouter surface of the ball receiving core and the inner surface of theball holding pipe, a projecting wall is formed at a part between thesubstantial flat outside part of the ball receiving portion of the ballreceiving core in the ball wrapping part, a ball surface part and theinner surface part of the ball holding pipe, and the ink capillaryguiding passage communicating with the ink passing space is formedbetween the ball receiving core and the ball surface part.

With this arrangement, the following advantages can be attained.

(1) The ball wedging action at the ball receiving part in the ballwrapping part is overcome and at the same time a circumference of theball surface in the ball wrapping part is uniformly enclosed with theink capillary guiding passage caused by the projecting wall so as toeliminate the presence of an ink capillary guiding vacant area, and thesurface of the ball in the ball wrapping part can be rotated better withless rotational resistance can be wet and wrapped with pooled ink undera capillary action between it and the ball surface. With thisarrangement, ink may not be drained back in the ball wrapping part, asuperior anti-drain back characteristic can be attained, an initialwriting can be preformed without any blurring of ink from the startingof a writing operation, the ink is guided up to the ball surface under acapillary action, a superior ink returning-back characteristic can beattained after an upward-directed orientation of the pen tip, a stablesupplying of ink and a rotating characteristic of ball are wellattained, no slippage of pen tip on the sheet surface due to aninsufficient rotation of the ball during a high-speed writing operationwill occur, and the supply of ink during high-speed writing can beassured.

(2) The above-described ball wrapping part and the ink passing space forcapillary guiding the ink to the ball wrapping part can easily be formedwith a combined assembly of the ball holding pipe and the ball receivingcore.

(3) The ink passing space at a sectional surface at a diameter in thepen tip is kept in the maximum capillary area in the limited range.

The present invention is made such that the projecting wall having theabove-described improved structure of the pen tip is formed at theoutside part of the ball receiving core.

With this arrangement, the following advantages can be attained.

(4) The projecting wall part can be formed relatively easily and highaccurately at the end surface of the ball receiving rod-like core by arolling machining or the like together with the ball receiving part,capillary intervals in the capillary guiding passage can correctly becontrolled and the capillary guiding capability of the ink is madeuniform in a superior manner.

The present invention is further made such that the projecting walls ofthe above-described improved pen tip structure are formed at the outsidepart of the ball receiving core and the inner surface of the ballholding pipe.

The following advantages can be attained.

(5) The projecting walls are separately arranged at the ball receivingcore and the ball holding pipe, a machining accuracy of each of them ishighly applied to get a high accuracy, so that the intervals of thecapillary guiding passages can be more accurately controlled and theguiding capability of the ink capillary action is highly uniformed. Theink is forcedly guided to the ball receiving part as lubricant agent anda more smooth rotation of the ball can be attained.

The present invention is made such that a cross sectional area of theink passing space of the above-described improved pen tip is made toshow a higher ratio without changing the interval of the ink capillaryportions that a cross sectional area of the capillary guiding passage.

With the foregoing arrangement, the following advantages can beattained.

(6) Amount of ink more than the comsumption volume of ink drawn from theball wrapping part with the ball can be guided from the ink passingspace to the capillary guiding passage in a capillary form and noblurring of ink caused by a lack of supplying of ink is found during ahigh-speed writing operation.

Further, the present invention is made such that the ink passing spacein the above-described improved pen tip structure is formed between theouter surface part of the ball receiving core of which diameter islarger than that of the ball and the inner surface of the ball holdingpipe facing to the outer surface.

With the above arrangement, the following advantages can be attained.

(7) An amount of ink exceeding over an amount of consumption of inkdrawn from the ball wrapping part with the ball can be supplied from theink passing space under a guiding of capillary action and at the sametime both an outer diameter of the outer surface of the ball receivingcore and an inner diameter of the ball holding pipe can easily becontrolled, a desired capillary interval can accurately be attained anda capability of the ink capillary guiding action is uniformly settled.

Further, the present invention is made such that the ink passing spaceof the above-described improved pen tip structure is formed between atapered outer surface of substantial trapezoid shape having a top endsurface of the ball receiving core facing to the ball receiving part andthe inner surface of the ball holding pipe which is parallel with theouter surface.

With this arrangement, the following advantages can be attained.

(8) An amount of ink exceeding over a consumption volume of ink drawnfrom the ball wrapping part with the ball can be supplied in capillaryguiding from the ink passing space and at the same time the inkcapillary guiding volume between the ink passing space and the capillaryguiding passage is gradually metered from the ink passing space to thecapillary guiding passage, so that the ink capillary movement is quitesmoothly performed and a controlled ink movement is also performed.

Further, the present invention is made such that an inner diameter ofthe ball holding pipe of the above-described improved pen tip structureis formed to a substantial same diameter as the ball diameter up to theink passing space forming part except the metering part preventing theball from being pulled out.

With this arrangement, the following advantages are attained.

(9) The pen tip having a diameter which is approximate to the balldiameter can be attained.

Further the present invention is made such that a sectional shape at adiameter of the inner surface of the ball holding pipe of theabove-described improved pen tip structure and a contour shape of asection at a diameter of the ball receiving core are formed in a similarshape.

With this arrangement, the following advantages are attained.

(10) A substantial balanced capillary action at each of the componentparts is made due to the fact that the intervals of each of the parts inthe ink passing space are similar to each other and then a superior inkguiding capability is attained.

Further, the present invention is made such that a sectional shape at adiameter of an inner surface of the ball holding pipe of theabove-described improved pen tip structure and a contuour shape at asectional surface of the ball receiving core are formed as circles.

With this arrangement, the following advantages are attained.

(11) Intervals at each of the parts of the ink passing space are madeequal, the ink guiding capability in the ink passing space are equal anda stable operation can be attained by each of the parts generating astable capillary action.

Further, the present invention is made such that an axial and spiralgroove is formed at a part where the ink passing space of an outersurface of the ball receiving core of the above-described improved pentip structure.

With this arrangement, the following advantages are attained.

(12) The axial straight flow of the ink is restricted, a superior inkyielding action is attained and a better anti-drain back characteristicof ink in the ink passing space is attained.

Further, the present invention is made such that circumferential annulargrooves are axially arranged in parallel at the ink passing spaceforming part of an outer surface of the ball receiving core of theabove-described improved pen tip structure.

With this arrangement, the following advantages are attained.

(13) A superior ink yielding in the ink passing space is attained and ananti-drain back characteristic of ink is further enforced.

Further, the present invention is made such that the ink capillaryguiding groove communicating with the ink passing space and reaching toa part near the ball receiving part is formed at an outside part of theball receiving core of the above-described improved pen tip structure.

With this arrangement, the following advantages are attained.

(14) The ink is forcedly capillary guided as lubricant agent from theink passing space to the ball receiving part so as to promote a smoothrotation of the ball.

Further, the present invention is made such that the ball receiving coreof the above-described improved pen tip structure is fixedly fitted inthe ball holding pipe.

With this arrangement, the following advantages are attained.

(15) The ball holding pipe and the ball receiving core are easilycoupled to make an integral structure.

Further, the present invention is made such that a fitting part of theabove-described improved pen tip structure is axially formed to have aprojecting shape.

With this arrangement, the following advantages are attained.

(16) A high bending strength of the pen tip under a wedging action ofthe fitting part is attained, a block-formed rectangular ink passingspace along the fitting part keeps an axial capillary action and asuperior ink guiding capability is attained.

Further, the present invention is made such that a fitting part of theabove-described improved pen tip structure is formed as a metering partextending in a circumferential direction.

With this arrangement, the following advantages are attained.

(17) Both axial and circumferential capillary actions in the ink passingspace are kept and a superior ink guiding capability is obtained.

Further, the present invention is made such that the ball of theabove-described improved pen tip structure is spherical.

With this arrangement, the following advantages are attained.

(18) There is no limitation in the writing process and the writing angleand a variety of applications, including writing, drawing and artificialhair lining such as eye shadow or eye brow writings are possible.

Further, the present invention is made such that the ball holding pipeand the ball receiving core of the above-described improved pen tipstructure are made of stainless steel and the ball is made of stainlesssteel or ceramics.

With this arrangement, the following advantages are attained.

(19) A high hardness is attained, a high durability is also obtained andfurther no corrosion caused by an electric potential, that is, noelectrostatic action results, rust formation due to electrostatic actionand a decreased capability of the ink guiding action due to rustclogging is eliminated and a non-variable ink guiding capability isretained.

Further, the present invention is made such that the ball holding pipeof the above-described improved pen tip structure is made of stainlesssteel, the ball is made of stainless steel or ceramics and the ballreceiving core is made by coating synthetic resin film on the sidesurface of the stainless core part, respectively.

With this arrangment, the following advantages are attained.

(20) A high hardness is attained, a sufficient durability is obtainedand at the same time no electrostatic action is generated and thedisadvantages caused by the electrostatic action are eliminated, aconstant ink guiding capability is kept and an ink wettingcharacteristic at a circumferential side surface of the ball receivingcore in the ink passing space is stabled at a high level.

Further, the present invention is made such that the capillary spacingsin the ink passing space of the above-described improved pen tipstructure are made to have an approximate value of 25 to 100μ.

With this arrangement, the following advantages are attained.

(21) A superior capillary action is performed and a moderate and stablevolume of ink is guided to the capillary guiding passage in the ballwrapping part.

Further, the present invention is made such that the intervals of thecapillary guiding passages of the above-described improved pen tipstructure are made to have an approximate value of 25 to 100μ.

With this arrangement, the following advantages are attained.

(22) A superior capillary action is obtained and a moderate and stableguiding of ink from the ink passing space to the ball surface isattained.

Further, the present invention is made such that a space between theopening edge of the metering part and the ball surface in theabove-described improved pen tip structure is made to have anapproximate value of 5 to 15μ.

With this arrangement, the following advantages are attained.

(23) The pen tip structure is properly controlled to have such a properdrawing degree as no ink dropping at the opening edge or no excessiveblurring of ink is made, a superior ink drawing is performed and the pentip is further controlled to hinder an air winding action caused by arotation of the ball, resulting in that an air winding is scarcely foundand therefore the ball surface is not applied with the winding air, butalways applied with ink in such a way as the ink is scraped with theball at its surface part.

Further, the present invention is made such that the capillary guidinggroove of the above-described improved pen tip structure is formed tohave a groove width of about 25 to 100μ and a groove depth of about 100to 20μ.

With this arrangement, the following advantages are attained.

(24) A superior capillary guiding of ink is performed from the inkpassing space to the ball receiving part.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate of the pen tip structure of thepresent invention.

FIG. 1 is a longitudinal sectional view through a pen tip structureaccording to one embodiment of the present invention.

FIG. 2 is a cross sectional view taken along a line (2)--(2) of FIG. 1.

FIG. 3 is a perspective view of the ball wrapping part at the lower endof the pen tip structure in FIG. 1, a portion of which is broken away.

FIGS. 4 to 9 are illustrative views of pen tip structures in which asectional shape at an inner surface of a ball holding pipe and a contourshape at a sectional surface at a diameter of a ball receiving core aresimilarly circular but wherein the projecting walls are different fromeach other FIGS. 4, 6 and 8 being longitudinal sections and

FIGS. 5, 7 and 9 being perspective views ball of the respective wrappingparts, portions of which are broken away.

FIGS. 10 to 18 illustrate pen tip structures in which a sectional shapeat a diameter of an inner surface of the ball holding pipe and a contourshape of a section at a diameter of the ball receiving core aresimilarly circular, the cross sectional area of the ink passing spacebeing larger than that of the capillary guiding passage, but wherein theprojecting walls is different from each other,

FIGS. 10, 13, 15 and 17 being longitudinal sections, FIG. 11 being across sectional view taken along a line (11)--(11) of FIG. 10, and FIGS.12, 14, 16 and 18 being perspective views of the respective ballwrapping parts, portions of which are broken away.

FIGS. 19 to 22 illustrate a pen tip structure in which a sectional shapeat a diameter of an inner surface of a ball holding pipe and a contourshape of a sectional shape at a diameter of a ball receiving core aresimilarly rectangular shape and the ball is in a roll form, FIG. 19being a longitudinal section, FIG. 20 being a cross sectional view takenalong a line (20)--(20), FIG. 21 being a perspective view of the ballwrapping part, a portion of which is broken away and FIG. 22 is aperspective view of the roll-form ball.

FIGS. 23 to 30 illustrate a pen tip structure in which a sectional shapeat a diameter of an inner surface of a ball holding pipe and a contourshape of a sectional surface of a ball receiving core are irregularlyshaped, FIGS. 23 and 27 being longitudinal sections, FIGS. 24 and 25being cross sectional views taken along lines (24)--(24) and (25)--(25)of FIG. 23, respectively, FIGS. 28 and 29 being cross sectional viewstaken along lines (28)--(28) and (29)--(29) of FIG. 27, respectively,and FIGS. 26 and 30 are perspective views of the respective ballwrapping parts, portions of which are broken away.

FIGS. 31 to 39 illustrate pen tip structures which include differenttypes of grooves in the outer surfaces of the ball receiving cores,FIGS. 31, 34 and 37 being longitudinal sections, FIG. 32 being a crosssectional view taken along a line (32)--(32) of FIG. 31, FIG. 35 being across sectional view taken along a line (35)--(35) of FIG. 34, FIG. 38being a cross sectional view taken along a line (38)--(38) of FIG. 7,FIGS. 33, 36 and 39 being perspective views of the respective ballwrapping parts, portions of which are broken away.

FIGS. 40 to 43 illustrate pen tip structures in which a capillaryguiding groove is arranged along an outside part of the ball wrappingpart, FIGS. 40 and 42 being longitudinal sections, FIGS. 41 and 43 beingperspective views of the respective ball wrapping parts, portions ofwhich are broken away.

FIGS. 44 to 46 are an illustration of a pen tip structure in which apress fitting between the ball holding pipe and the ball receiving coreis in substantially point form, FIG. 47 being a longitudinal section,FIG. 45 being cross sectional view taken along a line (45)--(45) of FIG.44, FIG. 46 being a perspective view of the ball wrapping part, aportion which is broken away.

FIG. 47 is a longitudinal section of a conventional type of pen tipstructure.

FIG. 48 is a longitudinal section of an experimental pen tip structurefor a comparison with the present invention.

FIGS. 49 to 52 are graphs showing the performance of ink flowing-outvolume in the present invention, the conventional type and theexperimental product, respectively, FIG. 49 illustrating the inkflowing-out volume in the pen tip structure of the present inventionshown in FIG.1, FIG. 50 illustrating the ink flowing-out volume in thepen tip structure of the present invention illustrated in FIG. 13, FIG.51 illustrating the ink flowing-out volume of the pen tip structure ofthe prior art shown in FIG. 47, and FIG. 52 illustrating the inkflowing-out volume of a pen tip structure of the experimental productshown in FIG. 48.

MOST PREFERRED EMBODIMENTS FOR PERFORMING THE INVENTION

Referring now to the drawings,

FIGS. 1 to 3 illustrate a basic pen tip structure according to thepresent invention. This pen tip is comprised of three componentelements: a ball holding pipe (1), a ball receiving core (2) fixed inthe ball holding pipe (1), and a ball (4) which is rotatably held in aball wrapping part (3) formed by the ball receiving core (2) in theextremity end of the ball holding pipe (1) and by the end surface part(2a).

The ball holding pipe (1) integrally stores a ball receiving core (2) ofsmall diameter of which ratio in respect to that of the ball holdingpipe is set to enable a clearance for capillary moving of ink to beformed between the inner surface of the ball holding pipe and the ballreceiving core with the proper locations of the ball holding pipe beingpress fitted to the core. An ink passing air path (5) is axially formedbetween an outside surface (6) of the ball receiving core (2) and theinner surface (7). An extremity inner end of the pipe is formed with aball wrapping part (3) having a bottom surface of an end surface part(2a) of the ball receiving core (2), thereby a ball (4) is rotatablystored in it. The ball is held by a metered part (14) of an opening edge(21) of the ball wrapping part (3) in such a way as the ball may not bedropped off the ball wrapping part (3). The press fitting portions (18)of the ball holding pipe (1) are in a projected belt type extending froma part near the end surface (2a) of the ball receiving core (2) to anaxially spaced-apart proper location while being circumferentiallyprojected under an axial equally spaced-apart relation. The ballreceiving core (2) is equally press fitted by the press fitting portionsat its circumference, the ball holding pipe (1) and the ball receivingcore (2) are integrally assembled with their bending strength i.e.rigidity being increased and at the same time the ink passing space (5)is made to have a uniform axial clearance and a uniform clearance in itsdirection of diameter. Since an ink adhering surface thickness of theball (4) is about 3 to 4μ, it is sufficient to have a capillaryclearance of the ink passing path (5) of at least more than 3 to 6μ. Itspractical value is about 25 to 100μ enabling a low viscosity ink to becapillary guided and this value is set in response to physicalproperties such as ink viscosity or the like.

The ball receiving core (2) is a solid component having a desireddiameter capable of forming the ink passing space (5) between it and theinner surface (7) of the ball holding pipe (1). At a central part of anend surface (2a) forming the bottom side in the ball wrapping part (3)is formed a substantial flat ball receiving part (8) to reduce therotational resistance of the ball (4) supported at a point on the ballreceiving portion (8). At an outside part (9) communicating with the inkpassing space (5) surrounding the ball receiving part (8) is formed anannular projecting wall (12) in such a way as an ink capillary guidingpath (13) is established between it and the surface (10) of the ball(4), thereby the ink is capillary guided from the ink passing space (5)to the capillary guiding path (13), i.e., the surface (10) of the ball(4) and stored in the capillary guiding path (13) at the surface part(10). Interval of the capillary tubes of the capillary guiding path (13)is approximately 25 to 100μ and this value is set in response tophysical properties such as viscosity of low viscosity ink or the like.

Further, the ball receiving part (8) in the ball receiving core (2) andthe projecting wall (12) may easily and high accurately be manufacturedby a rolling work or the like if their constituting material can beplastically machined, e.g. a metal.

The ball (4) is held in the ball wrapping part (3) with the metered part(14) at the extremity end of the ball holding pipe (1) so as not to bepulled off and as the ball is rotated, the ink is wiped from the inkpassing space (5) into the capillary guiding passage (13) with one ofthe surfaces (10) and then the ink is further wiped with the othersurface (10) and drawn out between the opening edge (21) of the meteredpart (14) and the ball surface. Diameter of the ball (4) is about 0.3 to1 mm and a space between the opening edge (21) and the surface of theball (4) is preferably about 5 to 15μ.

The projecting wall (12) in the ball wrapping part (3) is formed at itsoutside part (9) and/or inner surface part (11) at a location among theoutside part (9) of the ball receiving core (2), the surface part (10)of the ball (4) near the outside part and the inner surface part (11) ofthe ball holding pipe (1) in response to a capillary guiding capabilityof the capillary guiding path (13) and a lubricating capability under arotation of the ball or the like.

Similarly, the ink passing space (5) is set such that either a diameterratio or shape and constitution of the ball receiving core (2) inrespect to the ball (4) are selected in response to the variation ofconsumption volume of ink caused by a writing speed.

Similarly, the constituting material of the ball holding pipe (1) andthe ball receiving core (2) are selected from a combination of roundpipe and round rod, or a combination of rectangular pipe and rectangularrod, or a combination of round pipe and rectangular rod and acombination of rectangular pipe and round rod, respectively, in responseto a strength of the pen tip and a capillary guiding capability of theink passing space (5).

Similarly, the shape of the ball (4) is selected to have a spherical oneor a roll-form in response to its application.

Further, material quality of the ball holding pipe (1), ball receivingcore (2) and ball (4) is selected from metallic material such asstainless steel of SUS304 or the like, super engineering plastics suchas polyether ether ketone (PEEK), polyimide (PIM), polyphenilene sulfide(PPS) or the like and other plastic materials such as polyoxymethylene(POM), etc., and ceramic material in response to application,workability and electrostatic feature or the like.

For example, in case that the application is of a pen tip of a ball penor the like, the metallic material and ceramic material are preferableand in turn for application of make-up, a plastic material showing asoft touch is preferable. In view of the machining characteristic andink-proof characteristic, a stainless steel material of which rollingwork of plastic machining or the like is relatively easy and of whichanti-corrosion property is high is economically in preference and at thesame time it is preferable in respect to its electrostatic feature.

The above-described pen tip structure is closely fitted to a cap (23) ofa pen shaft (22) provided with an air hole (24), the end part of theball receiving core (2) is inserted into an ink intermediate core or inkimmersed body (25) composed of fibrous flux and the ink is suppliedthrough the ink capillary guiding action performed via ink capillaryguiding part (27) between the inner surface (26) of the cap (23) and theball receiving core (2).

FIGS. 4 to 9 illustrate a pen tip structure in which each of thepreferred embodiments of the projecting wall (12) of the presentinvention is different to each other and the remaining componentelements are basically the same as those of the earlier preferredembodiment. A sectional shape at a diameter of an inner surface of theball holding pipe (1) and a contour shape of a section at a diameter ofthe ball receiving core (2) are similarly circular.

FIGS. 4 and 5 illustrate the pen tip structure in which the projectingwall (12) of the present invention is made in an annular form at theinner surface part of the ball holding pipe (1), and the projecting wallpart (12) forms ink capillary guiding paths (13) communicated to eachother between the outside part (9) of the ball receiving core (2) andthe surface part (10) of the ball (4), respectively. The ink capillaryguided from the ink passing space (5) is passed and guided to the ballreceiving part (8), thereafter capillary guided to the surface part (10)so as to eliminate an ink capillary guiding vacant area at locationsamong the outside part (9), surface part (10) and inner surface part(11), and at the same time to lubricate a rotation of the ball (4).

FIGS. 6 and 7 illustrate the pen tip structure in which projecting walls(12) of the present invention are made in an annular form at each ofboth inner surface (11) of the ball holding pipe (1) and outside part(9) of the ball receiving core (2). Each of the projecting walls (12)form the ink capillary guiding passages (13) communicating to each otherbetween it and the surface part (10) of th ball (4) so as to guide apart of the ink capillary guided from the ink passing space (5) to theball receiving part (8) and further to eliminate the ink capillaryguiding vacant area among the outside part (9), surface part (10) andthe inner surface (11) and at the same time to lubricate the rotation ofthe ball (4).

FIGS. 8 and 9 illustrate the pen tip structure in which the projectingwall (12) of the present invention is metered in an annular form at theinner surface of the ball holding pipe (1). The projecting wall (12)forms an ink capillary guiding passage (13) between it and the surfacepart (10) of the ball (4) so as to feed and guide the ink capillaryguided from the ink passing space (5) to the ball receiving part (8),thereafter to capillary guide the ink to the surface part (10) andeliminate the ink capillary guiding vacant area at locations among theoutside part (9), surface part (10) and the inner surface part (11) andat the same time to lubricate the rotation of the ball (4).

FIGS. 10 to 18 illustrate the pen tip structure in which each of thepreferred embodiments having a larger cross sectional area of the inkpassing space (5) of the present invention than that of the capillaryguiding passage (13) without varying the interval of the capillary tubesis made different to each other and the remaining component elements arebasically the same as those of the earlier case. A sectional shape at adiameter of the inner surface of the ball holding pipe (11) and acontour shape at a section of a diameter of the ball receiving core (2)are similarly circular.

FIGS. 10 to 12 illustrate a pen tip structure in which the ink passingspace (5) of the present invention is formed between the outside part(6) of the ball receiving core (2) of which diameter is larger than thatof the ball (4) and the inner surface (7) of the ball holding pipe (1)facing to the outside part. This ink passing space (5) forms a crosssectional area larger than the capillary guiding passage (13) and anamount of ink exceeding over the amount of ink normally drawn from thecapillary guiding passage (13) by the ball (4) is capillary guided inresponse to the amount of drawing action and the amount of consumptionof the ink corresponding to the variation in writing speed is suppliedunder a capillary action.

FIGS. 13 to 18 illustrate a pen tip structure in which an ink passingspace (5) of the present invention is made to have a larger diameter ofthe ball receiving core (2) than that of the ball (4) and at the sametime it is formed between a tapered outer surface (6) of a substantialtrapezoid shape with a top end of the ball receiving part (8) and theinner surface (7) of the ball holding pipe (1) which is parallel to theouter surface. This ink passing space (5) is made such that a differencein a ratio of cross sectional areas of the ink passing space and thecapillary guiding passage (13) as the former is approached to thelatter. An amount of ink exceeding over an amount of ink normally drawnfrom the capillary guiding passage (13) with the ball (4) is capillaryguided in response to the amount of drawn ink and at the same time adifference between the ink guiding and supplying volumes in respect tothe capillary guiding passage is eliminated in a stepwise manner,thereby the amount of ink corresponding to the consumption amount of inkis always supplied in capillary action sufficiently even under a rapidvariation of the writing speed.

FIGS. 19 to 22 illustrate a pen tip structure in which a cross sectionalshape at a diameter of an inner surface of the ball holding pipe (1) ofthe present invention and a contour shape at a section of a diameter ofthe ball receiving core (2) are similarly rectangular, the ball (4) isin a roll form, and the remaining component elements are basically thesame as those of the earlier case. The ball holding pipe (1) is arectangular pipe and the ball receiving core (2) is a rectangular rod.

The projecting wall part (12) at the end surface (2a) of the ballreceiving core (2) is arranged around and along both sides of theroll-like ball (4) in parallel thereto and forms the ink capillaryguiding passage (13) between it and the surface (10) to eliminate theink capillary guiding vacant area at locations among the outside part(9), surface part (10) and the inner surface part (11). The pressfitting part (18) is a spot press fitting.

In this preferred embodiment, in particular a writing direction isprovided and a width of the roll corresponds to a writing width.

FIGS. 23 to 30 illustrate a pen tip structure in which a sectional shapeat a diameter of the inner surface of the ball holding pipe (1) of thepresent invention and the contour shape of a section at a diameter ofthe ball receiving core (2) are made in an irregular form and theremaining component elements are the same as those of the earlier case.

FIGS. 23 to 26 illustrate the pen tip structure in which a sectionalshape at a diameter of the inner surface of the ball holding pipe (1) ofthe present invention is a circular shape, a contour shape at a sectionat a diameter of the ball receiving core (2) is a rectangular shape,this round pipe and the rectangular rod are combined to each other, andthe remaining component elements are the same as those of the earliercase. The ball (4) is a spherical member.

The ink passing spaces (5) in this pen tip are separately andindependently divided in correspondence with the number of the outersurfaces (6) between the inner surface (7) of the ball holding pipe (1)and the outer surfaces (6) of the ball receiving core (2). The pressfitting part (18) is a planer metered press fitting in a circumferentialdirection.

FIGS. 27 to 30 illustrate the pen tip structure in which a sectionalshape at a diameter of the inner surface of the ball holding pipe (1) ofthe present invention is a rectangular form and a contour shape of asection at a diameter of the ball receiving core (2) is a circular form,this rectangular pipe and the round rod are combined to each other andthe remaining component elements are the same as those of the earliercase. The ball (4) at this pen tip is preferably a roll form and theprojecting wall portions (12) at the end surface part (2a) are arrangedat both sides of the surface part (10) of the roll-like ball (4) inparallel thereto and form between them and the surface part (10) the inkcapillary guiding passage (13).

Further, the ink passing spaces (5) are separately and independentlydivided in correspondence with the number of corners of the ball holdingpipe (1) between the inner surface (7) of each of the corners of theball holding pipe (1) of which sectional shape at its diameter part isrectangular form and the outer surface (6) of the ball receiving core(2) of which sectional shape at its diameter part is circle. The pressfitting part (18) is a planer metered press fitting in a circumferentialdirection.

FIGS. 31 to 36 illustrate the pen tip structure in which the outersurface (6) of the ball receiving core (2) of the present invention isformed as a single or a double spiral groove (15) and the remainingcomponent elements are basically the same as those of the earlier case.This spiral groove (15) forms the inner circumferential side of the inkpassing space (5) so as to restrict an axial straight flow of ink in thepassing space (5).

FIGS. 37 to 39 illustrate the pen tip structure in which the outersurface (6) of the ball receiving core (2) of the present invention isformed with axial parallel annular grooves (16) extending in acircumferential direction and the remaining component elements arebasically the same as those of the earlier case, the annular groove (16)forms the inner circumference of the ink passing space (5) so as torestrict an axial straight flow of the ink in the passing space (5).

FIGS. 40 to 43 illustrate a pen tip structure in which the outer surface(9) of the ball receiving core (2) of the present invention forms theink capillary guiding groove (17) and the remaining component elementsare basically the same as those of the earlier case. This capillaryguiding groove (17) is arranged at the outer side (9) extending up tothe ball receiving part (8) so as to capillary guide the ink from theink passing space (5) to the ball receiving part (8) and to improve thelubrication for a rotation of the ball (4) at the ball receiving part(8).

FIGS. 44 to 46 illustrate the pen tip structure in which the ballholding pipe (1) of the present invention is made of stainless steel,the ball receiving core (2) is made such that the side surface of thecore part (19) made of stainless steel is coated with synthetic resinfilm (20), the ball (4) is made of stainless steel and the remainingcomponent elements are basically the same as those of the earlier case.Also in this preferred embodiment, no electrostatic action is generatedamong the three component elements of the ball holding pipe (1), ballreceiving core (2) and the ball (4) and further both corrosion caused bythe electrostatic action and generation of rust are eliminated.

In the following table are described data obtained after a test of eachof the performances in relation to the pen tips of the pesent invention(FIGS. 1, 13 and 17), the pen tip of the prior art (FIG. 47) and the pentip of trial base for a comparison (FIG. 48).

A ball diameter of each of the pen tips is set as 0.6 φ and a viscosityof applied ink is 3 cp.

The pen tip of the prior art shown in FIG. 47 which is an item to betested has the same constitution as that of the pen tip of the presentinvention shown in FIG. 1 except a difference in presence ornon-presence of the ink capillary guiding vacant area in the ballwrapping part (3) and similarly the pen tip of the trial base shown inFIG. 48 has the same constitution as that of the pen tip of the presentinvention shown in FIG. 13 except a difference in presence ornon-presence of the ink capillary guiding vacant area in the ballwrapping part (3). Further, the pen tip of the present invention shownin FIG. 17 has the same constitution as that of the pen tip of thepresent invention shown in FIG. 13 except a difference in constitutionof the projecting wall (12).

The pen tip structure shown in FIG. 48 made in a trial base isconstructed such that an axial extending ink passing space (72) isformed between the ball holding pipe (70) and the ball receiving core(71) and fixed in it, a communicating part of the ball wrapping part(73) in the ink passing space (72) is formed between a substantialtrapezoidal tapered outer surface (75) having a top end of the flat ballreceiving part (74) in the ball receiving core (71) and the innersurface part (76) of the ball holding pipe (70) which is parallel to theouter surface part, the ball (77) is rotatably held in the ball wrappingpart (73), and the capillary guiding vacant area (82) showing no inkcapillary guiding is present in a space (81) among the circumferentialouter side part (78) of the ball receiving art (74), the surface part(79) of the ball (77) near the outer surface and the inner surface part(80) of the ball holding pipe (70).

    __________________________________________________________________________    Performance/Trial Product                                                                      FIG. 47                                                                            FIG. 1                                                                            FIG. 48                                                                            FIG. 13                                                                            FIG. 17                                   __________________________________________________________________________    Anti-drain back  X    ○                                                                          Δ                                                                            ⊚                                                                   ⊚                          Characteristic.sup.(1)                                                                         (70%)                                                                              (80%)                                                                             (75%)                                                                              (95%)                                                                              (95%)                                     Writing Condition                                                                         Vertical                                                                           ○                                                                           ○                                                                          ○                                                                           ○                                                                           ○                                              Writing                                                                       Slant                                                                              ○                                                                           ○                                                                          ○                                                                           ○                                                                           ○                                              Writing                                                           High-Speed       X    ○                                                                          Δ                                                                            ⊚                                                                   ○                                  Writing Characteristic.sup.(2)                                                Ink              Δ                                                                            ○                                                                          Δ                                                                            ○                                                                           ○                                  Discharging                                                                   Volume.sup. (3)                                                               Return Characteristic.sup.(4)                                                                  X    ○                                                                          Δ                                                                            ⊚                                                                   ⊚                                           (20%)                                                                              (40%)                                                                             (28%)                                                                              (60%)                                                                              (63%)                                     Initial          X    ○                                                                          Δ                                                                            ⊚                                                                   ⊚                          Writing           (4%)                                                                              (90%)                                                                             (42%)                                                                              (100%)                                                                             (100%)                                    Characteristic                                                                (Initial Writing).sup.(5)                                                     Writing Touch    ○                                                                           ○                                                                          ○                                                                           ○                                                                           ○                                  Working Characteristic                                                                    Metal                                                                              ⊚                                                                   Δ                                                                           ○                                                                           ⊚                                                                   Δ                                               Plastic                                                                            ⊚                                                                   ○                                                                          ○                                                                           ○                                                                           Δ                                               Ceramics                                                          __________________________________________________________________________

EVALUATION Excellent - ⊚ - ○ -Δ-x-Inferior

(1) A percentage of the number of pen tips of which upward directedwriting could be performed after the test product of which downwarddirected writing could be performed was left in a thermohygrostat of 60°C. for one week with its pen tip being directed upward.

(2) 60 cm/sec.

(3) Writing Speed: 4 m/min.; Writing Angle 65°; Writing Load: 100 g.

(4) A percentage of the number of the test products of which drain-backswere confirmed, where the downward directed writing could be performedafter being left in their downward directed condition.

(5) A percentage of the number of the test products in which they wereassembled to the main body of the pen, thereafter the test products weredirected downwardly in silence and left as they were for one hour andthen the inks were reached to the ball in their natural dropping action.

FIGS. 49 to 52 illustrate the ink discharging volume during writingoperation in respect to the data of the pen tip of the present invention(FIGS. 49 and 50) in which the ink capillary guiding vacant area is notpresent in the ball wrapping part (3) and the data of the pen tip inwhich the ink capillary guiding vacant area is present in the ballwrapping portions (53) and (73) (FIGS. 51 and 52) and five pen tipswhich were randomly selected were tested, respectively.

In view of the above table and data, it was confirmed that the pen tipstructure in which the ink capillary guiding vacant area is present inthe ball wrapping part was inferior in anti-drain back characteristic,high-speed writing, return characteristic and initial writingcharacteristics and much amount of disturbance were acknowledged in theink discharging volume.

In turn, the pen tip structure of the present invention in which the inkcapillary guiding vacant area is not present in the ball wrapping partis, as apparent from the table and data, superior in its anti-drain backcharacteristic, high-speed writing, return-back characteristic andinitial writing, and further it is confirmed that the disturbance in inkdischarging volume is decreased and made uniform and it shows a highreliability as a practical product.

APPLICABILITY IN THE INDUSTRY

As described above, the pen tip structure of the present invention isuseful for a writing, drawing and a make-up pen tip and in particular itis suitable for the application requiring a superior anti-drain backcharacteristic, a high-speed writing, ink discharging volume, areturn-back feature and initial writing and a durability against a highwriting pressure as well as a smooth rotation of the ball in particular.

What is claimed is:
 1. A pen tip structure which comprisesan elongatedcore which has a generally cylindrical outer surface, a first end forcontact with an ink-containing material and a second end for supportinga rotatable sphereical ball, said second end having a recess thereinshaped to provide a flat, circular center surface and an annularprojection surface which flares outwardly from the periphery of saidflat, circular center surface, a pipe which includes a shank portionpositioned around said elongated core and an end portion located beyondsaid second end of said elongated core, said shank portion of said pipedefining an inner surface and including a plurality of indentationstherein which contact the cylindrical outer surface of said elongatedcore and thereby provide a longitudinal ink flow channel between saidcylindrical outer surface of said elongated core and said inner surfaceof said shank portion of said pipe along which ink can flow by capillaryaction, said end portion of said pipe including an inwardly-extendingtip which provides a mouth for retaining a rotatable ball between saidtip and said second end of said elongated core, and a rotatable ballpositioned between said mouth of said pipe and said second end of saidelongated core, said rotatable ball having a surface, a first portion ofsaid surface extending beyond said mouth of said pipe and an opposite,second portion of said surface being in rubbing contact with said flat,circular center surface of said second end of said elongated core, saidrotatable ball having a diameter such that a gap is formed between saidsurface of said rotatable ball and said annular projection surface whichwill enable ink to pass therethrough from said ink flow channel to saidsurface of said rotatable ball by capillary action.
 2. A pen tipstructure according to claim 1, wherein said annular projection surfaceat said second end of said elongated core extends to said generallycylindrical outer surface thereof.
 3. A pen tip structure according toclaim 2, wherein said annular projection surface is straight in crosssection.
 4. A pen tip structure according to claim 1, wherein saidsecond end of said elongated core includes an annular, inwardly-slopedouter surface portion which merges with said annular projection surface.5. A pen tip structure according to claim 4, wherein said inner surfaceof said pipe forms an annular lip which extends towards said secondsurface portion of said rotatable ball adjacent said second end of saidelongated core, said annular lip and said annular, inwardly-sloped outersurface portion of said elongated core forming an annular connectingchannel which enables ink to flow by capillary action from said ink flowchannel to said gap and to said second surface portion of said rotatableball.
 6. A pen tip structure according to claim 4, wherein said secondend of said elongated core includes a plurality of radially-extendinggrooves which extend from said annular, inwardly-sloped outer surfaceportion to said annular projection surface, said radially-extendinggrooves having a width that enable ink to flow therethrough by capillaryaction.
 7. A pen tip structure according to claim 1, wherein each ofsaid plurality of indentations in said shank portion of said pipe extendaxially of said pipe.
 8. A pen tip structure according to claim 1,wherein the radial spacing between said cylindrical outer surface ofsaid elongated core and said inner surface of said pipe is between 25and 110 μ.
 9. A pen tip structure according to claim 1, wherein thespacing between said rotatable ball and said annular projection surfaceat said second end of said elongated core does not exceed 100 μ.
 10. Apen tip structure according to claim 1, wherein said elongated core iscomposed of stainless steel.
 11. A pen tip structure according to claim10, wherein said rotatable ball is composed of stainless steel.
 12. Apen tip structure according to claim 10, wherein said rotatable memberis composed of a ceramic material.
 13. A pen tip structure according toclaim 10, wherein said pipe is composed of stainless steel.
 14. A pentip structure according to claim 10, including a resin coating on saidcylindrical outer surface of said elongated core.
 15. A pen tipstructure according to claim 1, wherein said tip at said end portion ofsaid pipe is spaced from said ball by 5 to 15 μ.
 16. A pen tip structureaccording to claim 1, wherein said second end of said elongated coreincludes a plurality of radially-extending grooves which extend fromsaid cylindrical outer surface thereof through said annular projectionsurface, said radially-extending grooves having a width that enables inkto flow therethrough by capillary action.
 17. A pen tip structureaccording to claim 1, wherein said elongated core has an outer diameterwhich is substantially equal to the diameter of said ball.
 18. A pen tipstructure according to claim 1, wherein said elongated core has an outerdiameter which is larger than the diameter of said ball.
 19. A pen tipstructure according to claim 1, wherein each of said plurality ofindentations in said shank portion of said pipe extend circumferentiallyof said pipe.
 20. A pen tip structure according to claim 1, wherein thegenerally cylindrical outer surface of said elongated core includes asingle axial spiral groove therein.
 21. A pen tip structure according toclaim 1, wherein the generally cylindrical outer surface of saidelongated core includes a double axial spiral groove therein.
 22. A pentip structure according to claim 1, wherein the generally cylindricalouter surface of said elongated core includes a plurality ofaxially-spaced annular grooves therein.